Light guide plate is a critical member in a backlight module. At present, the light guide plate is generally manufactured by injection moulding. A mould is necessarily used in the injection moulding and a mould core is a key component in the mould. For an optical-grade light guide plate, an optical-grade mirror mould core is necessarily used. In general, the mirror mould core is machined by polishing. Therefore, the quality of the mould core depends on the quality of polishing.
In the process of polishing, a polishing machine and a polishing clamp are necessarily used to polish a work-piece to be processed. The polishing clamp is configured to fix the work-piece to be processed and regulate process conditions. A chuck is generally used in the polishing clamp in the prior art. As shown in FIG. 1, the chuck 11 is fixed to the work-piece to be processed (herein referring to a mould core 12) by screws. When being processed, the mould core 12 is positioned on the polishing machine (not shown) with its machined surface down.
In current processing manners, a portion of the mould core 12 may be slightly caught into polishing buff or polishing cloth due to the gravity action of the chuck 11. With a long-time polishing process, an over-wearing may occur at edges and/or corners of the machining surface of the mould core 12 as circled in FIG. 2. When the light guide plate is injection-moulded, the edge of the light guide plate may be unsmooth with the use of the mould core having above deficiency, thereby degrading the quality of the light guide plate.